Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
It is generally know that the efficiency and power coefficient of a typical open wind turbine, i.e. a wind turbine without any coverings or other performance enhancing apparatus, is limited by the Betz limit. However, various apparatus have been included on wind turbines to exceed the Betz limit and thus increase the efficiency and power coefficient of the wind turbine.
For example, shroud apparatus have been included on wind turbines. One approach is to utilize a shroud having a diameter that exceeds the total outer diameter of the rotor blades, such that the rotor blades fit within the shroud. Another approach is to connect a portion of the shroud to the tip of each of the rotor blades. During operation, the shrouds cause the air flow past the rotor blades to increase, allowing the rotor blades to extract more energy and thus increasing the efficiency and power coefficient of the wind turbine.
However, such known shrouds have various disadvantages. For example, as wind turbines and the associated rotor blades increase in size, the shrouds must additionally increase in size in order for the rotor blades to fit within, or in order for the shroud portions mounted to the rotor blade tips to function adequately. However, such increases in size may require prohibitive amounts of materials and expenses.
Accordingly, improved shrouds for wind turbines and methods for modifying the performance of wind turbines would be desired. For example, an improved shroud and method for increasing the performance of a wind turbine would be advantageous.